The invention relates to a device for stopping a carrier traveling in a pneumatic transmission line and also to a terminal for a pneumatic transmission line. The invention may be used in various types of pneumatic transmission systems and is especially useful in systems that operate at lower speeds.
Pneumatic transmission systems are widely known and used to transmit articles from one place to a remote location. Pneumatic transmission or delivery systems consist of tubes or conduits in which a carrier containing information travels by means of pneumatic pressure. The pressure may be provided by a blower and/or vacuum system. A common use of pneumatic transmission systems is in drive-in bank tellers where business is conducted by a carrier transmitted between the bank and a remote terminal. Other uses for pneumatic transmission systems include sending documents between floors in a building or from one office to another office located some distance apart. Pneumatic transmission systems that are capable of operating at slower speeds may be used in transmitting blood samples and other more "fragile" cargo.
In previous pneumatic transmission systems, a problem existed in stopping the carrier once it reached its intended location. In many systems, the carrier, traveling at speeds of 15-20 ft/sec or higher, impacts a mechanical trigger that shuts off the blower or vacuum, and the carrier continues to a second impact with a stop or block at the end of the transmission line. The carrier bounces off the stop and is caught by the same mechanical trigger or some other catch device. In these systems, the carrier and mechanical trigger are subjected to impacts that are highly undesirable and that results in wear and tear on the carrier and the trigger mechanism. The use of a mechanical trigger to shutoff the pneumatic source requires that the carrier be traveling at a high enough speed to actuate the trigger. Thus, the higher speed required to activate the trigger causes a greater impact. The high speed and resulting impact eliminates the possibility of using such systems to transmit "fragile" articles such as blood samples.
Some systems have designed a deceleration zone in which the carrier decelerates prior to entering the terminal area and impacting an end stop. One such system is disclosed in U.S. Pat. No. 4,180,354 to Greene, the disclosure of which is incorporated herein by reference. Greene discloses a transmission system using a check valve that reroutes the air behind the carrier and allows the carrier sufficient time to decelerate before discharging into an open remote terminal. Other attempts to resolve the problem of the impact have included the use of other mechanical means in place of the trigger to shutoff the stream of air. These include items such as a photocell, a timing device, limit switch, spring catch, and combinations thereof.
The present invention provides a new and different means for stopping the carrier and shutting off the pneumatic source. The invention does not use a mechanical trigger or timing device, and it eliminates the need for an extended deceleration region prior to the terminal. The present invention further allows operation of the carrier at much slower speeds, and thus, the system is better able to transport "fragile" articles.